Oaten was unseated on an electoral petition on 6 October 1997. The High Court held that 54 votes declared void for want of the Official Mark would have changed the result if counted. The court could not be sure they were not the product of a mistake, therefore deemed that the result was uncertain. They allowed the petition and declared the election void. The writ for the new election was moved on 28 October 1997.[1]

The by-election on 20 November resulted in a clear win by Oaten – his majority was 21,556 over second-placed Gerry Malone, the former Conservative MP who had lost his seat in the general election.

Campaigning had focused on Oaten's speaking record in the House of Commons after the general election,[2] while the nature of the controversial 1 May election result was also an issue for some Liberal Democrat voters. The Independent wrote, "Although careful not to articulate it themselves, their unofficial campaign slogan is: 'When the umpire gives you out, you should walk'",[2] alluding to the unseated Malone.

The Labour Party obtained their worst ever results in a parliamentary election, in part because they hardly campaigned at all and instead focused their priorities on the by-election in Beckenham held on the same day.

Screaming Lord Sutch, candidate in the by-election

Both the original and rerun election involved an incidence of a candidate using an attempted confusing description. Richard Huggett described himself in the general election as Liberal Democrat Top Choice For Parliament (leading to Oaten, the official Lib Dem candidate, to use the ballot paper description Liberal Democrat Leader Paddy Ashdown) and in the by-election as Literal Democrat Mark Here to Win. The Registration of Political Parties Act 1998 put an end to this practice.